Low Temperature n-alkanes Bromination without Catalysts

It has been observed that Ba (BrF₄)₂ demonstrated a high reactivity towards normal alkanes from C₆H₁₄ to C₁₆H₃₄. It has been found that the reactions ran with intensive self-heating and release of elemental bromine. The GC-MS analysis showed that the main product of Ba (BrF₄)₂ interaction with each alkane was its 3-bromoderivative. The optimal interaction parameters have been found. The heat effects of the reaction have been determined by the isothermal calorimetric method, it has been found that the heat effect of the bromination increased with the increase of the length of carbon chain of alkane.     

Optimization and modeling of synthesis parameters of neodymium(III) bromide by dry method using full factorial design analysis

The synthesis of neodymium(III) bromide (NdBr₃) by sintering brominating of neodymium oxide (Nd₂O₃) with ammonium bromide (NH₄Br) was investigated. The influence of various synthesis parameters (temperature, contact time and stoichiometry) on the reaction yield was studied and optimized. The main interaction effects of the synthesis parameters on the reaction yield were also determined by a full 2³ factorial designs with six replicates at the center point.This study showed that the optimum conditions for the synthesis of NdBr₃ are following: contact time t = 60 min, stoichiometry in moles Nd₂O₃:NH₄Br = 1:24 and temperature T = 400 °C. The reaction yield for these parameters was equal to 97.80%. The first order model was obtained to predict the reaction yield as a function of these three parameters. It was shown that all parameters have a significant positive influence on reaction yield. In addition it was pointed out also that the interaction effects between them are significant.     

Ga(ClO4)3-catalyzed synthesis of quinoxalines by cycloaddition of α-hydroxyketones and o-phenylenediamines

A new approach for the synthesis of 2-substituted quinoxalines by Ga(ClO₄)₃-catalyzed cycloaddition of α-hydroxyketones and o-phenylenediamines is introduced. The reaction is catalyzed by 10 mol % of Ga(ClO₄)₃ in EtOH at room temperature. It is performed under simple and mild conditions to afford the product in good yield.     

Neutron powder diffraction study and B-site ordering in microwave dielectric ceramics Ba(Ca1/3Nb2/3)O3

Microwave dielectric powder Ba(Ca_1/3Nb_2/3)O₃ with high B-site cation ordering was synthesized by the molten salt method. Neutron powder diffraction (NPD) and Raman scattering spectra were introduced to investigate the variable ordering degree during the sintering process. It was revealed that the as-synthesized Ba(Ca_1/3Nb_2/3)O₃ powder had a nearly completely ordered structure, and the sintered Ba(Ca_1/3Nb_2/3)O₃ presented a bit higher ordering degree based on the detailed quantitative NPD Rietveld full profile fitting. The complete Raman mode assignment for the Ba(Ca_1/3Nb_2/3)O₃ was presented. The phonon bands could also confirm the order–disorder structural model and increasing ordering degree with the increasing sintering temperature. Final microwave dielectric measurements on sintered samples showed the present compound to tailor other dielectric materials for microwave applications with the dielectric properties of ?_r = 47.11, and Qf = 1389 GHz, and τ_f was about 113 ppm/°C.     

Electrochemical kinetics of the hydrogen reaction on platinum in concentrated HCl(aq)

The hydrogen reaction in concentrated HCl(aq) solutions is a key reaction for the CuCl(aq)/HCl(aq) electrolytic cell. Here, electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) were used to obtain new data for the hydrogen reaction on platinum submerged in highly concentrated acidic solutions at 25 °C and 0.1 MPa. LSV and EIS data were collected for Pt in 0.5 mol/L H₂SO₄(aq), 1 mol/L HCl(aq) and 7.71 mol/L HCl(aq) solutions. It was found that exchange current density (j₀) values varied between 1 and 2 mA/cm². An equivalent circuit model was used to obtain comparable j₀ and limiting current density values from EIS data relative to values obtained with LSV data. It was found that as the concentration of acid increased, a noticeable decrease in the performance was observed.     

Li2SO4-polyacrylamide polymer electrolytes for 2.0 V solid symmetric supercapacitors

A neutral polymer electrolyte comprised of lithium sulfate (Li₂SO₄) and polyacrylamide (PAM) was developed. The Li₂SO₄-PAM electrolyte film shows an ionic conductivity up to 10 mS cm^− 1 in 45%RH conditions. Solid double layer capacitors were demonstrated using CNT-graphite electrodes and Li₂SO₄-PAM solid electrolytes. The voltage window of the solid cell was about 2.0 V, identical to that of a Li₂SO₄ liquid cell used as baseline. The demonstrated voltage window is significantly larger than that reported for proton- or hydroxyl-conducting electrolytes, suggesting that the Li₂SO₄-PAM electrolyte is a promising system for high energy density supercapacitors. The solid device also demonstrated excellent rate capability (up to 5 V s^− 1) and good cycle life (beyond 10,000 charge/discharge cycles).     

Reduced-dimensionality and direct trajectory calculations for the C(3PJ) + NH2(2B1) reaction

Nonadiabatic transitions through spin–orbit interaction for the C(³P_J) + H₂(²B₁) reaction were investigated by ab initio electronic structure calculations and quantum reactive scattering calculations. It has been found that the reactivity for the J = 0 and J = 1 states is quite large. Ab initio direct trajectory calculations on the lowest doublet potential energy surface have also been carried out in order to understand the HNC production mechanism. We have found that HNC is mostly produced via direct mechanism, in which the H elimination occurs directly from the CNH₂ intermediate, initially formed by the addition of C to NH₂.     

Direct ab initio molecular dynamics study of the two photodissociation channels of formic acid

A total of ∼1200 trajectories have been integrated for the two photodissociation channels of formic acid, HCOOH → H₂O + CO (1) and HCOOH → CO₂ + H₂ (2), which occur with 248 and 193 nm photons, using the direct ab initio molecular dynamics method at the RMP2(full)/cc-pVDZ level of theory. It was found that the percentage of the energy distributed to a relative translational mode in reaction (2) is much larger than that in reaction (1). This is mainly due to the difference in the geometry of transition state (TS); the H₂O geometry in the TS of reaction (1) was predicted to significantly deviate from the equilibrium one, whereas the CO₂ and H₂ geometries in the TS of reaction (2) were found to be more similar to their equilibrium ones. It was also found that the product diatomic molecules, CO and H₂, are both vibrationally and rotationally excited. The calculated relative population of the vibrationally excited CO for the 248 nm photodissociation was consistent with experiment.     

Synthesis,spectroscopic, magnetic and thermal properties of bimetallic salts, [Ni(L)][MCl4] {where M = Co(II), Zn(II), Hg(II) and L = 3,7-bis(2-aminoethyl)-1,3,5,7-tetraazabicyclo(3.3.1)nonane}. X-ray structure of [Ni(L)][CoCl4]

New bimetallic complex salts corresponding to the formulation [Ni(L)][MCl₄] have been synthesized by the facile reaction between [Ni(L)](ClO₄)₂ and [MCl₂(PPh₃)₂] in high yields {where M = Co(II), Zn(II), Hg(II) and L = 3,7-bis(2-aminoethyl)-1,3,5,7-tetraazabicyclo(3.3.1)nonane}. The complexes were characterized by IR, electronic spectra, TGA/DSC, magnetic moment and conductivity measurements. The X-ray crystal structure for [Ni(L)][CoCl₄] clearly establishes the cationic–anionic interaction. It crystallizes in the space group P1 with unit cell dimensions a = 7.1740(15) Å, b = 8.1583(16) Å and c = 8.3102(16) Å. A square-planar geometry is evident for the [Ni(L)]²⁺ cation while the anion is found to be tetrahedral. A two-step thermolytic pattern is observed in the pyrolysis of the bimetallic complex salts.     

Thermodynamic properties of calcium titanates: CaTiO3, Ca4Ti3O10, and Ca3Ti2O7

The chemical potentials of CaO in two-phase fields (TiO₂ + CaTiO₃), (CaTiO₃ + Ca₄Ti₃O₁₀), and (Ca₄Ti₃O₁₀ + Ca₃Ti₂O₇) of the pseudo-binary system (CaO + TiO₂) have been measured in the temperature range (900 to 1250) K, relative to pure CaO as the reference state, using solid-state galvanic cells incorporating single crystal CaF₂ as the solid electrolyte. The cells were operated under pure oxygen at ambient pressure. The standard Gibbs free energies of formation of calcium titanates, CaTiO₃, Ca₄Ti₃O₁₀, and Ca₃Ti₂O₇, from their component binary oxides were derived from the reversible e.m.f.s. The results can be summarised by the following equations: CaO(solid) + TiO₂(solid) → CaTiO₃(solid), ΔG° ± 85/(J · mol^?1) = ?80,140 ? 6.302(T/K); 4CaO(solid) + 3TiO₂(solid) → Ca₄Ti₃O₁₀(solid), ΔG° ± 275/(J · mol^?1) = ?243,473 ? 25.758(T/K); 3CaO(solid) + 2TiO₂(solid) → Ca₃Ti₂O₇(solid), ΔG° ± 185/(J · mol^?1) = ?164,217 ? 16.838(T/K).The reference state for solid TiO₂ is the rutile form. The results of this study are in good agreement with thermodynamic data for CaTiO₃ reported in the literature. For Ca₄Ti₃O₁₀ Gibbs free energy of formation obtained in this study differs significantly from that reported by Taylor and Schmalzried at T = 873 K. For Ca₃Ti₂O₇ experimental measurements are not available in the literature for direct comparison with the results obtained in this study. Nevertheless, the standard entropy for Ca₃Ti₂O₇ at T = 298.15 K estimated from the results of this study using the Neumann–Koop rule is in fair agreement with the value obtained from low-temperature heat capacity measurements.     

Halogenation of Lewis acid/base stabilised phosphanylboranes

The reaction pattern of the Lewis-acid/base stabilised phosphanylborane [(CO)₅W(H₂PBH₂ · NMe₃)] (1) with elemental halogens is comprehensively studied. The reaction with iodine and bromine leads to a selective halogenation at the tungstencarbonyl moiety under formation of [WX₂(CO)₄(H₂PBH₂ · NMe₃)] (X = I (2), Br (3)). Whereas 2 is a stable product the brominated compound 3 dimerises easily to [WBr₂(CO)₃(H₂PBH₂ · NMe₃)]₂ (4) under lost of CO. The CO elimination reaction of 3 is extensively studied. If 3 is reacted with [Et₄N][Br] the ionic compound [Et₄N][WBr₃(CO)₃(H₂PBH₂ · NMe₃)] (5) is formed. Otherwise, if 3 is combined with the donor ligand [H₂PBH₂ · NMe₃], the complex [WBr₂(CO)₃(H₂PBH₂ · NMe₃)₂] (6) is obtained. Compounds 2–6 are comprehensively characterised by X-ray diffraction analysis, NMR, and IR spectroscopy.     

In situ synthesis of composite MTiO3–Al2O3 coatings via laser zone melting

Laser zone melting was employed in this work to prepare MTiO₃ based coatings over commercial, polycrystalline Al₂O₃ substrates, using the corresponding mixtures of powdered alkaline earth carbonates and TiO₂ as starting materials. In situ synthesis of the series M = Ca, Sr, Ba was studied using a CO₂ laser as the heating source, emitting at 10.6 μm, following substrate preheating to a temperature of 750 °C and sample displacement speed of 500 mm h⁻¹. Microstructure (SEM) and phase composition (XRD) demonstrated in situ formation of crystalline MTiO₃ perovskite (M = Ca, Sr), MAl₂O₄ (M = Ca), MAl₁₂O₁₉ magnetoplumbite type (M = Sr) and MAl₁₄O₂₂ β-alumina type (M = Ba) phases. Substantial interaction with the substrate resulted in stable, 50–150 μm thick, composite coatings.     

Spectroscopic investigation of the interaction of p-benzoquinone with casein in the solid state

The reaction between p-benzoquinone (PBQ) and casein (protein) in the solid state was studied. After reaction with protein, the FT-IR spectra showed a new band at 1215 cm^?1, with an intense sign attributed for casein/PBQ product. An optimum amount of PBQ for determination of the product when mixed with casein was 100 mg and a reaction time of 30 min. The product was stable for a period of 24 h after the reacting by heating. The interaction of PBQ with casein was investigated by FT-IR, reflectance, Raman and EPR spectroscopies. The reaction between PBQ and casein in the solid state yields a radical species (p-benzosemiquinone) that it is stabilized by the presence of p-biphenolate and p-benzoquinone species in the solid state.     

Thermodynamic evaluation and optimization of the (NaNO3 + KNO3 + Na2SO4 + K2SO4) system

A complete critical evaluation of all available phase diagram and thermodynamic data has been performed for all condensed phases of the (NaNO₃ + KNO₃ + Na₂SO₄ + K₂SO₄) ternary reciprocal system, and optimised model parameters have been found. The model parameters obtained for the four binary common-ion subsystems (i.e. (NaNO₃ + Na₂SO₄), (KNO₃ + K₂SO₄), (NaNO₃ + KNO₃) and (Na₂SO₄ + K₂SO₄)) are used to predict thermodynamic properties and phase equilibria for the entire system. The Modified Quasichemical Model in the Quadruplet Approximation for short-range ordering was used for the molten salt phase, and the Compound Energy Formalism was used for the various solid solutions.     

(Solid + liquid) isothermal evaporation phase equilibria in the aqueous ternary system (Li2SO4 + MgSO4 + H2O) at T = 308.15 K

The solubility and the density in the aqueous ternary system (Li₂SO₄ + MgSO₄ + H₂O) at T = 308.15 K were determined by the isothermal evaporation. Our experimental results permitted the construction of the phase diagram and the plot of density against composition. It was found that there is one eutectic point for (Li₂SO₄ · H₂O + MgSO₄ · 7H₂O), two univariant curves, and two crystallization regions corresponding to lithium sulphate monohydrate (Li₂SO₄ · H₂O) and epsomite (MgSO₄ · 7H₂O). The system belongs to a simple co-saturated type, and neither double salts nor solid solution was found. Based on the Pitzer ion-interaction model and its extended HW models of aqueous electrolyte solution, the solubility of the ternary system at T = 308.15 K has been calculated. The predicted solubility agrees well with the experimental values.     

Thermodynamic evaluation and optimization of the (NaCl + KCl + MgCl2 + CaCl2 + MnCl2 + FeCl2 + CoCl2 + NiCl2) system

A complete critical evaluation of all available phase diagram and thermodynamic data has been performed for all condensed phases of the (NaCl + KCl + MgCl₂ + CaCl₂ + MnCl₂ + FeCl₂ + CoCl₂ + NiCl₂) system, and optimized model parameters have been found. The (MgCl₂ + CaCl₂ + MnCl₂ + FeCl₂ + CoCl₂ + NiCl₂) subsystem has been critically evaluated in a previous article. The model parameters obtained for the binary subsystems can be used to predict thermodynamic properties and phase equilibria for the multicomponent system. The Modified Quasichemical Model was used for the molten salt phase, and the (MgCl₂ + MnCl₂ + FeCl₂ + CoCl₂ + NiCl₂) solid solution was modeled using a cationic substitutional model with an ideal entropy and an excess Gibbs free energy expressed as a polynomial in the component mole fractions. Finally, the (Na,K)(Mg,Ca,Mn,Fe,Co,Ni)Cl₃ and the (Na,K)₂(Mg,Mn,Fe,Co,Ni)Cl₄ solid solutions were modeled using the Compound Energy Formalism.     

Mechanochemical synthesis and ionic conductivity of lanthanum phosphosilicate oxyapatites

Lanthanum phosphosilicate apatites with the chemical formula Sr_10–xLa_x(PO₄)_6–x(SiO₄)_xO, where 0 ≤ x ≤ 6, usually prepared by a solid-state reaction at about 1400 °C, were synthesized via the mechanochemical method at room temperature. The samples were characterized using powder X-ray diffraction, infrared spectroscopy and thermal analysis. The results showed that the prepared products were carbonated apatites and no secondary phase was detected. The realization of the milling under a controlled atmosphere can lead to oxyapatites containing no carbonates. The ionic conductivity of the Sr₆La₄(PO₄)₂(SiO₄)₄O sample was investigated by using impedance spectroscopy. The highest ionic conductivity value of 1.522 × 10⁻⁶ S·cm⁻¹ was found at 800 °C. In the investigated temperature range, the activation energy is of 0.85 eV.     

Solvent-free asymmetric direct aldol reactions organocatalysed by recoverable (Sa)-binam-l-prolinamide

The combination of (S_a)-binam-l-Pro (5 mol %) and benzoic acid (10 mol %) was used as catalysts in the direct aldol reaction between different aliphatic ketones and 4-nitrobenzaldehyde under solvent-free reaction conditions. Three different procedures are assayed: magnetic stirring (method A), magnetic stirring after previous dissolution in THF and evaporation (method B), and ball mill technique (method C), methods A and B being the simplest. These reaction conditions allowed us to reduce the amount of required ketone to 2 equiv to give the aldol product in similar reaction times and regio-, diastero-, and enantioselectivities than in organic or aqueous solvents.     

Fabrication and electrochemical performance of nickel ferrite nanoparticles as anode material in lithium ion batteries

Nano-sized nickel ferrite (NiFe₂O₄) was prepared by hydrothermal method at low temperature. The crystalline phase, morphology and specific surface area (BET) of the resultant samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and nitrogen physical adsorption, respectively. The particle sizes of the resulting NiFe₂O₄ samples were in the range of 5–15 nm. The electrochemical performance of NiFe₂O₄ nanoparticles as the anodic material in lithium ion batteries was tested. It was found that the first discharge capacity of the anode made from NiFe₂O₄ nanoparticles could reach a very high value of 1314 mAh g⁻¹, while the discharge capacity decreased to 790.8 mAh g⁻¹ and 709.0 mAh g⁻¹ at a current density of 0.2 mA cm⁻² after 2 and 3 cycles, respectively. The BET surface area is up to 111.4 m² g⁻¹. The reaction mechanism between lithium and nickel ferrite was also discussed based on the results of cycle voltammetry (CV) experiments.     

Spin dimer analysis of the magnetic structures of A2V3O9 (A = Ba,Sr) and η-Na9V14O35: Importance of the V4+–O⋯O–V4+ super-superexchange interactions mediated by the O–V5+–O bridges

Spin dimer analysis was carried out for the magnetic oxides of V⁴⁺ (d¹) ions, A₂V₃O₉ (A = Ba, Sr) and η-Na₉V₁₄O₃₅, to account for their magnetic structures. After identifying the V(O_eq)₄ square planes containing the magnetic orbitals of the V⁴⁺ (d¹) ions, we analyzed the relative strengths of the various V–O_eq–V and V–O_eq⋯O_eq–V spin exchange interactions. The V–O_eq⋯O_eq–V spin exchange interactions mediated by O_eq–V⁵⁺–O_eq bridges are found to be crucial in determining the magnetic structures of A₂V₃O₉ (A = Ba, Sr) and η-Na₉V₁₄O₃₅. Our analysis suggests that η-Na₉V₁₄O₃₅ should have two different spin gaps.